1. Field of the Invention
The present invention relates to a method for synthesizing an organometallic compound, and in more detail, relates to an efficient and low cost method for synthesizing an organometallic compound usefully utilized as a catalyst for polyolefin manufacturing by ring-opening metathesis polymerization of an olefin having strain in a molecule such as dicyclopentadiene or synthesis of epothilones by ring-closing metathesis reaction, by using an easily available starting material due to relatively simple chemical structure.
2. Description of the Prior Art
A reaction using a transition metal compound has been utilized, by a catalytic action of a metal complex thereof, in wide fields ranging from synthesis of low molecular weight compounds such as medicines to synthesis of polymers such as highly functional plastics.
For example, polymerization of ethylene or propylene by Ziegler-Natta catalysts consisting of titanium tetrachloride or titanium trichloride and alkyl aluminum, polymerization to obtain uniform polyolefin by Kaminsky catalysts consisting of zirconocene and methylaluminoxane, organic metathesis reactions by transition metal carbene catalysts and the like, are well known.
Recently, transition metal carbene catalysts, in particular, ruthenium carbene catalyst is attracting attention. Ruthenium carbene catalyst is a compound having a Ru═C bond in a molecule (a bond between a ruthenium atom and divalent carbon atom without charge) and, in particular, dichloro-hydrogen-phenyl-carbene-bis(tri-cyclohexyl-phosphine)ruthenium, typically shown by [(Cl2Ru═CHPh)(PCy3)2] has been developed by Grabs group of California Institute of technology and disclosed in JP-A-11-510807, JP-A-11-262667, and the like.
This compound has been found to show superior metathesis catalytic activity without deactivation even in the presence of moisture or oxygen and being not labile to a functional group in the metathesis reaction substrate, and utilized in ring-closing metathesis synthesis of various monomers useful as medicine and the like, or in manufacturing molded articles with superior mechanical strength, heat resistance, dimensional stability, and the like, by ring-opening polymerization of a norbornene type monomer, including dicyclopentadiene (hereinafter, may be abbreviated as DCPD), a typical monomer used in the metathesis polymerization, in a mold by a reactive injection molding method (hereinafter, may be abbreviated as RIM) and the like. Thus, the compound is used and attracts attention in various wide industrial fields.
However, since this catalyst is not activated in a reaction system with an alkyl metal and the like, but has an activity as a single complex, there is a problem that the reaction spontaneously starts as soon as the catalyst is added to a monomer with metathesis reactivity, and thereby dispersion of the catalyst and the like determines the reaction rate. This tendency may be a fatal problem in polymerization of a crosslinkable monomer such as dicyclopentadiene, it causes problems such as serious limitation on a process or variation of physical properties of a polymer obtained.
To overcome this problem, a method of adding triphenylphosphine or the like to a reaction system to retard polymerization is generally known. However, it also has a problem of product safety due to contamination of impurities such as phosphorus in the system.
As a catalyst to solve the above-described problems, dichloro-hydrogen-phenyl-thio-carbene-bis(tri-cyclohexyl-phosphine)ruthenium, typically shown by [(Cl2Ru═CHSPh)(PCy3)2] has been disclosed in WO 99/00396. This patent also discloses such compounds whose sulfur atom is substituted with an oxygen atom, an imino group or a phosphine-di-yl group, in the above-described chemical formula of this catalyst.
This catalyst is very superior, but a synthesis method thereof, as shown in a) and b) of Example 1 in the page 33 of said official gazette, has problems. Namely, in the case of a), a raw material itself has a complicated chemical structure such as RuCl2[P(C6H11)3]2(═CH—CrH5), and thus requires many steps in preparation, while in the case of b), a raw material, ruthenium dichloride(cis,cis-cyclopentadiene), although the chemical structure itself is simple, must be reacted with 1,8-diazabicyclo[5.4.0]undeca-7-ene and tricyclohexylphosphine, both having complicated chemical structures, in isopropanol at 80° C. for 1 hour, followed by reacting at −20° C. for 1 hour, further adding 1 mole of a solution of diethyl ether hydrochloride, stirring for 15 minutes and further adding 1-hexyne and phenyl vinyl sulfide, to synthesize the target substance, thus requiring use of many expensive raw materials and making the synthesis complicated with many reaction steps as well as disadvantageous in cost.
A method for synthesizing a hetero carbene complex such as RuCl2[P(C6H11)3]2(═CH—S—) generally includes, for example, as shown in “Chemistry. Letters”, 1999, 369 or “Organometallics”, 2002, 21, 2153–2164, a reaction of a conventional alkylidene complex with a vinylhetero compound such as vinyl sulfide, followed by exchanging a vinyl moiety. However, heteroalkylidene complexes synthesized by these synthesis methods have a residual vinylhetero compound from the raw material or a vinyl compound exchanged due to co-existence in the system, and it is generally known that the complex synthesized inhibits the metathesis reaction by these remaining compounds.
Therefore, in the method for synthesizing a hetero carbene complex by the vinyl exchange requires complete removal of these vinyl compounds from the system. To solve such problems, it is necessary to repeat a washing step many times after isolation. However, additional unnecessary washing step or accompanying decrease in yield is not preferable from the industrial point of view.